Electric stove



Jan. 28, 1964 P. SCHLUMBOHM 3,119,923

ELECTRIC STOVE Filed Jan. 10, 1962 Fl6.4 F165 INVENTOR' M m l/WM Patented .ian. 28, 1964 3,119,923 ELEQTRIC STOVE Peter Sclilunibohm, 41 Murray St., New York, N.Y.; (Iirancis. German, executor of said Peter Schluinbohm,

ecease Filed Jan. 10, 1962, Ser. No. 165,361 1 Claim. (8]. 219-34) This invention relates to an electric stove of a type useful also as an air heater for heating rooms and more particularly to an improved stove of this type and including the characteristic of low resistance low temperature heating elements.

Most conventional electric heaters are of the high temperature element type depending mainly upon radiation for the transfer of heat and provided with switch means for low, medium and high heat output. Such conventional heaters adjusted to low produce insufiicient watts output to be of appreciable use in heating a room and when adjusted to other settings produce a heating element temperature sufficiently high to cause undesirable odors of burnt dust and chemical changes as well as a fire hazard.

Efforts to avoid this situation have resulted in water filled radiators with built in immersion heaters and other devices directed to low temperature heat transfer.

It is an object of my invention to provide an improved, efficient, effective and reliable low temperature heat transfer stove providing maximum heating and heat transfer in a compact unit.

A further object is to provide a stove of the above type in which the heating elements are formed, supported, and arranged one with respect to the other to provide maximum heat transfer and maximum convection of air therethrough while avoiding the development of hot spots in the unit.

Briefly summarized the invention comprises the provision helically wound coils of resistance wire selected as to material, cross-section and length to provide a desired wattage output when connected to a given voltage supply and a maximum heat transfer area, the supporting and spacing of the coils in a chimney like body to provide a strong convection air current and uniform heating of moving air and the short circuiting of adjacent turns passing through supports to avoid the development of hot spots.

In one stove unit following my invention I have found that for an output of 1500 Watts at 120 volt source a resistance Wire of Nichrome #11 having a diameter of .091 and an uncoiled length of about 150 will provide the necessary ohms resistance and under normal operating conditions produces an air current of approximately 300 F.

The wire is wound into a helical coil on a mandrel and mounted within a chimney with the various coil windings being arranged and spaced to prevent reheating air in its passage through the chimney and each coil is supported by passing through spaced metallic tubular support elements which short circuit adjacent turns at the support and thus avoid hot spots.

The tubular elements are mounted on straps formed of vertically sliced strips of a cylinder identical to that cylinder which forms the stove body such that the straps and stove body have the same curvature.

The open ends of the stove body are closed by perforated grid plates, the perforations representing about 50% of the surface to allow sufiicient air flow. The stove body is supported on legs to allow entry of air at the bottom.

Further details, objects and advantages of the invention will become apparent from the following specification and from the drawings illustrating one example of the invention. In the drawings:

FIG. 1 is a side view shown partly in view and partly in vertical cross section.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is a top view of FIG. 1 with a covering top grid partly broken away.

FIG. 4 is a side view of a detail element of FIG. 1.

FIG. 5 is a frontal view of FIG. 4, away.

PK}. 6 shows a detail element, partly in view and partly in vertical cross section.

FIG. 7 is a view of a detail shown in vertical cross section.

FIG. Sis a top view of FIG. 6.

FIG. 9 is atop view of FIG. 7.

Referring to the drawings which show a preformed embodiment of my invention, in FIGURE 1 numeral 1 indicates a fiberglass barrel which as shown is mounted on three legs by bolts or other suitable means and is provided with a perforated top grill 9 and perforated bottom grid h. The perrorated grill 9 and grid 9' are mounted respectively on the top and bottom of the cylindrical barrel or body portion of the stove by angle members 7 which are secured to the barrel body by bolts 8 and 8'.

As shown in FiGURES 6 through 9 of the preferred embodiment the top grid 9 is provided with prongs projecting vertically and of equal length so that the bottom of a pan may rest on them without closing the grid perforations to the flow of air. The prongs may be solid pieces 13 as in FIGURE 6, or may be tubular pieces 14 apertured as at 15 in the wall thereof for air passage, as shown in FZGURE 7. The prongs may be secured to the grid 9 by any suitable means as for example grooves in the prong to receive the edge portions of an associated hole in the grid 9, as shown in FIGURES 6 and 7.

As shown in FIGURE 2 since the stove is intended as a portable multipurpose unit for room heating and for cooking handles 12 are bolted or otherwise secured to the body of the stove to carry the stove from one location to another, it being understood that the complete stove weighs about nine pounds. Also provided as shown in FKGURE 2 is a conventional electric plug 11 mounted through the wall of the stove body for connection to a source of electric power for the heating elements of the stove now to be described.

As shown in FIGURES l, 3, 4 and 5 the heating element comprises a helically wound coil of wire 16 of spaced adjacent turns and selected of material and cross-section in relation to the voltage to be imposed on said wire to limit the temperature of air fiow through the stove body under normal operating conditions to a maximum of 490 F.

To support the wire 14) within and in electrically insulated relation to the hollow body 1 of the stove I provide a plurality of vertically positioned elongated strips 3 of non-conducting material secured as by cementing or other suitable means in spaced relation along the inner periphery of the body 1. Such strips, as previously mentioned may be cut from tubular stock used to form the body 1 such that the curvature of the strips mate substantially with the curvature of the body.

Secured to the strips 3 as by rivets 6 or other suitable means I provide tubular ring elements 4 to support the wire coil 16). Also as shown in FIGURES 1, 3, 4 and 5 I provide additional tubular ring elements 5 carried by associated elements 4 to support portions of the coil 10 in an inwardly disposed position from adjacent portions thereof to be cooled by air which has not become preheated by passing over a coil section supported at a lower level by elements 4. In order not to complicate the drawings, they have been limited to the example of ring elements 4 and 5 and to showing two different diameters of the coil within the stove body 1. However, it is to be understood that this offset mounting can be executed in other variations to supply the coil section at an upper level with air which has not been too much preheated by coil sections at a lower level.

Since a basic desire in performance according to the invention is to provide in a compact portable unit a maximum development and transfer of heat under condition of a predetermined temperature limit to thereby obtain and maintain the inherent benefits of this form of heat development and transfer, all as previously explained herein, it is desirable to include in the combination of elements means for avoiding the development of hot spots in the stove unit. To this end the rings 4 and 5 are made conductive to the extent that each ring short circuits adjacent turns of the coil 10 passing therethrough. It is understood, or"- course, that rings 5 mounted on associated rings 4 are electrically insulated from each other by suitable means (not shown) to the end that adjacent coils of the heating element 110 are not short circuited. It is desirable simply to short circuit adjacent turns of a coil passing through a supporting ring.

From the above it will be apparent that invention is not directed simply to the selection of one size or material of wire in place of another. It is directed to the selecting, arranging and combining of the various elements described into an electrical stove providing maximum transfer of heat under the temperature limitation mentioned with the attendant advantages.

Having fully described my invention and shown by way of example the manner in which it may be performed, what I claim as new and desire to secure by Letters Patent is:

An electric stove comprising in combination a body portion having a hollow interior, side enclosure and an open top and bottom portion to form a vertical air passageway, support means for said body portion arranged to admit air to said open bottom portion, resistance wire means formed of a vertically arranged helically wound coil of spaced adjacent turns positioned in said passageway to produce when electrically energized a vertical flow of warmed air, said wire means being of selected material and cross-section in relation to the voltage to be imposed on said Wire means to limit the temperature of said air flow to a maximum of 400 F. under normal operating ambient temperature of less than 70 F., means for supporting said wire means in said passageway and in electrically insulated relation to said body portion of said stove, said wire supporting means including a plurality of vertically positioned elongated strips of non-conducting material secured to the inner surface of said side enclosure, a plurality of vertically spaced tubular elements fixed to each of said vertical wardiy from adjacent portions thereof.

References Cited in the file of this patent UNITED STATES PATENTS 864,518 Cruickshank Aug. 27, 1907 1,119,841 Kuhn Dec. 8, 1914 1,161,667 Hays Nov. 23, 1915 1,320,155 Kuhn et al, Oct. 28, 1919 1,322,701 Kuhn et al. Nov. 25, 1919 1,392,868 Cruickshank Oct. 4, 1921 1,719,872 Calcott July 9, 1929 1,983,862 Maness et a1 Dec. 11, 1934 2,268,233 Wilson et al. Dec. 30, 1941 2,740,033 Perrine et al. Mar. 27, 1956 FOREIGN PATENTS 265,279 Great Britain Feb. 2, 1927 536,820 Great Britain May 28, 1941 633,284 Great Britain Dec. 12, 1949 721,657 France Dec. 22, 1931 

